1. Field of the Invention
This invention relates to the recovery of the titanium values in titaniferous materials and more particularly to recovery of such values by chlorination techniques.
While chlorination techniques for recovery of the titanium values in titaniferous materials have proved successful, such techniques are most successful when limited to the use of titaniferous materials rather depleted in iron content. Use of ferruginous titaniferous materials, such as ilmenites or the like, complicates recovery of the titanium values from the material because of the affinity of chlorine to attack the iron values initially, causing formation of unwanted iron chlorides. The art is replete in theoretical and practical teachings on practice of such chlorination techniques and little need be stated here for the artisans of this field, except that the need for economic and efficient recovery of the titanium values of titaniferous material uncomplicated by iron chloride formation yet exists.
2. Description of the Prior Art
The art is virtually silent in proposing to selectively chlorinate the titanium values of the titaniferous material with Cl.sub.2 whereby substantially no iron chloride is formed. Perhaps the only proposal in this area is that of Wilcox (U.S. Pat. No. 2,589,466) wherein an ilmenite ore and chlorine gas, each separately preheated to about 1250.degree.-1500.degree. C., are fed to a chlorination zone maintained within such temperature range and wherefrom substantially pure titanium tetrachloride vapors are withdrawn, while substantially all the iron content of the feed ore remains in the solid residue in the chlorination zone.
Of more recent vintage are the proposals of Glaeser (U.S. Pat. Nos. 3,977,862; 3,977,863; 3,977,864 and 4,017,304) wherein titaniferous materials, such as ilmenite, are selectively chlorinated at about 950.degree. to 1400.degree. C. for removal of TiCl.sub.4 without an appreciable net yield of iron chloride from the iron constituent of the feed ore and whereby such iron constituent is recoverable in the metallic state. Such selective chlorination is accomplished with chlorinating agents of ferrous chloride, ferrous chloride and Cl.sub.2, ferrous chloride and HCl, and HCl in combination with at least two of the following members of the group consisting of FeCl.sub.2, FeCl.sub.3, and Cl.sub.2. Also of more recent vintage is the proposal of Othmer (U.S. Pat. No. 3,989,510) wherein the selective chlorination of the titanium constituent of the ore is accomplished by charging a hot chlorinator (1535.degree.-1950.degree. C.) with the ore, silica, alkali metal or alkaline earth metal chloride, and carbonaceous reductant. Products formed are vaporous TiCl.sub.4, molten metallic iron, and molten silicate flux containing various of the ore impurities.
Of significance, too, is the total chlorination process. A total chlorination process comprises chlorinating the iron-bearing titaniferous material at elevated temperature with chlorine gas in at least stoichiometric proportion for formation of titanium tetrachloride and iron chlorides. The disadvantages of total chlorination techniques are obvious and include loss of chlorine in the form of iron chlorides, contamination of product titanium tetrachloride stream with iron chlorides, and a substantial waste disposal problem of such iron chlorides formed in the process.
Heretofore, it has been accepted principle in this art that when chlorinating ferruginous titaniferous ores with Cl.sub.2, all (or substantially all) of the iron must be chlorinated first before any of the titanium can be chlorinated. Total chlorination processes as above-described are based upon this principle. The present invention, though, permits chlorination of the titanium in the ferruginous titaniferous feedstock to occur while concomitantly converting at least some of the iron in the feed to metallic iron, i.e. suppression of iron chloride formation.